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NAT is described in general terms in RFC 1631. which discusses NAT's relationship to
Classless Interdomain Routing (CIDR) as a way to reduce the IP address depletion problem.
NAT reduces the need for a large amount of publicly known IP addresses by creating a
separation between publicly known and privately known IP addresses. CIDR aggregates
publicly known IP addresses into blocks so that fewer IP addresses are wasted. In the end,
both extend the use of IPv4 IP addresses for a few more years before IPv6 is generally
supported.
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NetBEUI, NetBIOS Extended User Interface, is a new extended
version of NetBIOS, the program that lets computers communicate within a local area
network. NetBEUI (pronounced net-BOO-ee) formalizes the frame format (or arrangement of
information in a data transmission) that was not specified as part of NetBIOS. NetBEUI was
developed by IBM for its LAN Manager product and has been adopted by Microsoft for its
Windows NT, LAN Manager, and Windows for Workgroups products. Hewlett-Packard and DEC use
it in comparable products.
NetBEUI is the best performance choice for communication within a single LAN. Because,
like NetBIOS, it does not support the routing of messages to other networks, its interface
must be adapted to other protocols such as Internetwork Packet Exchange or TCP/IP. A
recommended method is to install both NetBEUI and TCP/IP in each computer and set the
server up to use NetBEUI for communication within the LAN and TCP/IP for communication
beyond the LAN.
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NetBIOS, Network Basic Input/Output System, is a program that
allows applications on different computers to communicate within a local area network
(LAN). It was created by IBM for its early PC Network, was adopted by Microsoft, and has
since become a de facto industry standard. NetBIOS is used in Ethernet, token ring, and
Windows NT networks. It does not in itself support a routing mechanism so applications
communicating on a wide area network (WAN) must use another "transport
mechanism" (such as Transmission Control Protocol) rather than or in addition to
NetBIOS.
NetBIOS frees the application from having to understand the details of the network,
including error recovery (in session mode). A NetBIOS request is provided in the form of a
Network Control Block (NCB) which, among other things, specifies a message location and
the name of a destination.
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NETMASK is a string of 0's and 1's that mask or screen out the
network part of an IP address (IP) so that only the host computer part of the address
remains. The binary 1's at the beginning of the mask turn the network ID part of the IP
address into 0's. The binary 0's that follow allow the host ID to remain. A
frequently-used netmask is 255.255.255.0. (255 is the decimal equivalent of a binary
string of eight ones.) Used for a Class C subnet (one with up to 255 host computers), the
".0" in the "255.255.255.0" netmask allows the specific host computer
address to be visible.
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NETSCAPE is one of the two most popular Web browser and also
the name of a company, Netscape Communications, now owned by America Online (AOL).
Currently, almost all Internet users use either Netscape's browser or Microsoft's Internet
Explorer (MSIE) browser, and many users use both. Although Netscape was initially the
predominant product in terms of usability and number of users, Microsoft's browser is now
considered superior by many users (although many other users see them as roughly
equivalent) and has taken a slight lead in usage.
Netscape's browser originally was called "Navigator," and is still called that
in the suite of software, Communicator, of which it is now a part. Navigator was developed
in 1995 by a team led by Marc Andreessen, who created Mosaic, the first Web browser that
had a graphical user interface, at the University of Illinois' National Center for
Supercomputing Applications (NCSA) in 1993.
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NETWORK, a series of points or node interconnected by
communication paths. Networks can interconnect with other networks and contain
subnetworks.
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NAS Network Access Server, is a computer server that enables an
independent service provider (ISP) to provide connected customers with Internet access . A
network access server has interfaces to both the local telecommunication service provider
such as the phone company and to the Internet backbone.
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NETWORK ENCRYPTION (sometimes called network layer,
or network level encryption) is a network security process that applies crypto services at
the network transfer layer - above the data link level, but below the application level.
The network transfer layers are layers 3 and 4 of the Open Systems Interconnection (OSI)
reference model, the layers responsible for connectivity and routing between two end
points. Using the existing network services and application software, network encryption
is invisible to the end user and operates independently of any other encryption processes
used. Data is encrypted only while in transit, existing as plaintext on the originating
and receiving hosts.
Network encryption is implemented through Internet Protocol Security (IPsec), a set of
open Internet Engineering Task Force (IETF)standards that, used in conjunction, create a
framework for private communication over IP networks. IPSec works through the network
architecture, which means that end users and applications don't need to be altered in any
way. Encrypted packets appear to be identical to unencrypted packets and are easily routed
through any IP network.
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NIC Network Interface Card, is a computer circuit board or card
that is installed in a computer so that it can be connected to a network. Personal
computers and workstations on a local area network (LAN) typically contain a network
interface card specifically designed for the LAN transmission technology, such as Ethernet
or token ring. Network interface cards provide a dedicated, full-time connection to a
network. Most home and portable computers connect to the Internet through as-needed
dial-up connection. The modem provides the connection interface to the Internet service
provider.
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NETWORK LAYER In the Open Systems Interconnection (OSI)
communications model, the Network layer knows the address of the neighboring nodes in the
network, packages output with the correct network address information, selects routes and
Quality of Service, and recognizes and forwards to the Transport layer incoming messages
for local host domains. Among existing protocol that generally map to the OSI network
layer are the Internet Protocol (IP) part of TCP/IP and NetWare IPX/SPX. Both IP Version 4
and IP Version 6 (IPv6) map to the OSI network layer.
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NOS Network Operating System, is a computer operating system system
that is designed primarily to support workstation , personal computer , and, in some
instances, older terminal that are connected on a local area network (LAN. Artisoft's
LANtastic, Banyan VINES, Novell's NetWare, and Microsoft's LAN Manager are examples of
network operating systems. In addition, some multi-purpose operating systems, such as
Windows NT and Digital's OpenVMS come with capabilities that enable them to be described
as a network operating system.
A network operating system provides printer sharing, common file system and database
sharing, application sharing, and the ability to manage a network name directory,
security, and other housekeeping aspects of a network.
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NOC Network Operations Center, is a place from which a
telecommunications network is supervised, monitored, and maintained. An enterprise with
large networks as well as large network service providers such as GTE Internetworking
typically have a network operations center, a room containing visualizations of the
network or networks that are being monitored, workstations at which the detailed status of
the network can be seen, and the necessary software to manage the networks. The network
operations center is the focal point for network troubleshooting, software distribution
and updating, router and domain name management, performance monitoring, and coordination
with affiliated networks.
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NSP Network Service Provider, is a company that provides backbone
services to an Internet service provider (ISP), the company that most Web users use for
access to the Internet. Typically, an ISP connects at a point called an Internet Exchange
(IX) to a regional ISP that in turn connects to an NSP backbone. In the U.S., major NSPs
include MCI, Sprint, UUNET, AGIS, and BBN.
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NETWORKING is the construction, design, and use of network,
including the physical (cabling, hub, bridge, switch, router, and so forth), the selection
and use of telecommunication protocol and computer software for using and managing the
network, and the establishment of operation policies and procedures related to the
network.
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NODE is a connection point, either a redistribution point or an
end point for data transmissions. In general, a node has programmed or engineered
capability to recognize and process or forward transmissions to other nodes.
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nslookup is the name of a program that lets an Internet server
administrator or user enter a host name (for example, "whatis.com") and find out
the corresponding IP address. It will also do reverse name lookup and find the host name
for an IP address you specify.
For example, if you entered "cnsny.net", you would receive as a response our IP
address, which happens to be :
65.215.31.31
Or if you entered "65.215.31.31", it would return "cnsny.net".
nslookup sends a domain name query packet to a designated (or defaulted) domain name
system (DNS) server. Depending on the system you are using, the default may be the local
DNS name server at your service provider, some intermediate name server, or the root
server system for the entire domain name system hierarchy.
Using the Linux and possibly other versions of nslookup, you can locate other information
associated with the host name or IP address, such as associated mail services. nslookup is
often included with a UNIX-based operating system. Free versions exist that can be added
to Windows operating systems. A more limited alternative to nslookup for looking up an IP
address is the ping command.
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